light - Longest and shortest wavelength

Well, I don't think this question is entirely answerable. The true answer, I think, is that there really are no limits, as Rob Jeffries commented.

However, using Wikipedia as my only source, the crab pulsar holds the current record for most energetic gamma ray emissions at 80 TeV (wavelength of about $1.5times10^{-11}$nm).

Whereas the longest detected wavelength would surely only be limited by our detector sensitivity. Any imaginable wavelength could be lengthened further by an arbitrary factor via, for example, scattering.

EDIT: Source: Gamma-ray Astronomy (Wikipedia)